THE WELCOME OF THE FLOWERS 



397 



of white flowers a considerably larger proportion smell sweetly than of 

 any other colour namely, 14'6 per cent. ; of red, only 8'2 per cent, are 

 odoriferous. The fact of a larger proportion of white flowers smelling 

 sweetly may depend 

 in part on those 

 which are fertilized 

 by moths requiring 

 the double aid of 

 conspicuousness in 

 the dark and of 

 odour. So great is 

 the economy of 

 Nature, that most 

 flowers which are 

 fertilized by crepu- 

 scular or nocturnal 

 insects emit their 

 odour chiefly or ex- 

 clusively in the 

 evening. Some 

 flowers, however, 

 which are highly 

 odoriferous, depend 

 solely on this quality 

 for their fertiliza- 

 tion, such as the 

 night-flowering 

 Stock (Hesp&ria) and 

 some species of 

 Daphne ; and these 

 present the rare 

 example of flowers 

 which are fertilized 

 by insects being 

 obscurely coloured." 

 Conspicuousness 

 and Odour usually 

 go together, but this 

 is not always the 

 case. The flowers of 

 the Willow, Lime, and Mignonette are notable exceptions. The hypantho- 

 dium of the Fig is another. What attracts the wasp to the Fig? Not 

 the brightness of its densely packed unisexual flowers, for they are hidden 

 quite out of sight. It is the odour. Were it not for the odour the 



by] [. Step. 



FIG. 488. WOOD SPURGE (Euphorbia amygdaloides). 



A larger species than the Petty Spurge, and a perennial. The horns of the nectar 

 glands converge in this species. 



